The rapid progress of corn planting sometimes can outpace the application of soil-residual herbicides. In most instances these herbicides are applied within a few days after planting, but weather-and equipment-related factors can delay applications until after corn has emerged.
Most, but not all, soil residual herbicides can be applied after corn has emerged. Products such as Balance Pro, Radius, Fierce, Prequel, Sharpen and Verdict must be applied before corn begins to emerge; applications of these products to emerged corn can result in significant corn injury. Be cautious about applying a soil-residual herbicide in UAN carrier if corn has emerged as this can increase the potential for corn injury. Also, be sure to consult the respective product label for tankmix and spray additive recommendations or prohibitions.
Labels usually indicate a maximum corn growth stage beyond which applications should not occur. These growth stages can range from as early as two leaf collars to as late as 40-inch tall corn, so be sure to consult the respective product labels. Products containing atrazine must be applied before corn exceeds 12-inches tall, although the labels of some atrazine-containing products specify a smaller height.